1. Infrasound Technology Workshop – Tokyo, November 2007 1 Listen to the Sounds of the Antarctic Atmosphere L. Ceranna, A. Le Pichon & E. Blanc BGR / B3.11, Hannover, Germany CEA / DASE, Bruyères-le-Châtel, France

2. Infrasound Technology Workshop – Tokyo, November 2007 2 Content   The Antarctic Infrasound Array I27DE  Observations and Signal Detections at I27DE  Conclusions  Future Work Design and Configuration Noise Reduction and Performance Infrasound: Microbaroms and Mountain Associated Waves Gravity Waves Neumayer III Electric Power Generation using Wind Turbines Reconfiguration of I27DE

3. Infrasound Technology Workshop – Tokyo, November 2007 3 Location of infrasound station I27DE 5°W10 °W 71 °S 72 °S Satellite Image of the Ekström Ice Shelf

4. Infrasound Technology Workshop – Tokyo, November 2007 4 Site map of I27DE

5. Infrasound Technology Workshop – Tokyo, November 2007 5 Array responses for two 9-element configurations ‘Pinwheel‘ Configuration Concentric ConfigurationArray Response Co-Array

6. Infrasound Technology Workshop – Tokyo, November 2007 6 Design and installation of hose arrays 16 arms: 90 and 70 m aperture 32 arms: 70 and 50 m aperture 16 arms: 70 and 50 m aperture

7. Infrasound Technology Workshop – Tokyo, November 2007 7 The effect of wind Comparison of different noise levels depending on wind speed

8. Infrasound Technology Workshop – Tokyo, November 2007 8 Comparison of different noise levels depending on the rate of snow accumulation on top of the pipe arrays Noise reduction by snow coverage

9. Infrasound Technology Workshop – Tokyo, November 2007 9 Array performance as a function of wind speed PMCC analysis in frequency range from 0.05 to 4 Hz, Jan-2003 – Dec-2005 mb-signals, [0.05 0.7] Hz detection threshold hf-signals, [0.7 4.0] Hz detection threshold

10. Infrasound Technology Workshop – Tokyo, November 2007 10 Detection of hf- and mb-signals, Mar-2003 – Sep-2007 ~365,000 hf-detections, ~515,000-mb detections

11. Infrasound Technology Workshop – Tokyo, November 2007 11 Average radial stratospheric wind speeds, HWM-93 motion of ocean swells along peri-Antarctic belt

12. Infrasound Technology Workshop – Tokyo, November 2007 12 Amplitudes of mb-signals, Mar-2003 – Sep-2007

13. Infrasound Technology Workshop – Tokyo, November 2007 13 Trace velocities of mb-signals, Mar-2003 – Sep-2007

14. Infrasound Technology Workshop – Tokyo, November 2007 14 Amplitudes of mw-signals, Mar-2003 – Sep-2007 ~41,000 mw-detections

15. Infrasound Technology Workshop – Tokyo, November 2007 15 Trace velocities of mw-signals, Mar-2003 – Sep-2007

16. Infrasound Technology Workshop – Tokyo, November 2007 16 Amplitudes of gw-signals, Mar-2003 – Sep-2007 ~50,000 gw-detections

17. Infrasound Technology Workshop – Tokyo, November 2007 17 Trace velocities of gw-signals, Mar-2003 – Sep-2007

18. Infrasound Technology Workshop – Tokyo, November 2007 18 Example of gravity waves – bores at I27DE

19. Infrasound Technology Workshop – Tokyo, November 2007 19 Comparison of detected signals, August/September 2004 wind microbaroms mountain associated waves gravity waves infrasound mb and maw signals are (completely) decoupled infrasound signals and gravity waves are not correlated trace velocity of gw signals indicates limits of infrasound detection capability maw: V T {gw} < 10 m/s; mb: V T {gw} < 20 m/s are measured wind and gw signals correlated?!

20. Infrasound Technology Workshop – Tokyo, November 2007 20 Wave parameters of gravity waves and measured wind β=82°±22° V T =17±7 m/s A=0.16 Pa β=238°±14° V T =9±6 m/s A=0.09 Pa

21. Infrasound Technology Workshop – Tokyo, November 2007 21  I27DE has demonstrated that its configuration and design are well suited for high wind conditions. It has been operated for more than 4.5 years without any major problems.  The average detection threshold of mb-signals can be estimated at wind speeds of 16 m/s, i.e., at almost 85 % of the time I27DE have the capability to detect infrasound signals showing typical mb-signal amplitudes.  Detection of mb-signals correlates well with a stable stratospheric duct obtained with HWM-93 showing easterly directions during the Antarctic summer (December & January) and westerly at other time of the year.  An anomaly in the number of detections and trace velocity was observed for mb-signals during the Antarctic winter, the reason for probable absence of the stratospheric duct is currently not clear.  mw-Signals are decoupled from mb detections in winter times, however regard during Antarctic summer mw detections are dominated by mb-signals. Moreover another source, being independent of stratospheric duct, exists in the direction of ~120°. Conclusions I

22. Infrasound Technology Workshop – Tokyo, November 2007 22  gw-signals are showing large amplitudes (gwE: 0.16 Pa, gwW: 0.09 Pa). These signals are NOT correlated to the stratospheric duct.  gw-signals are correlated to measured wind speed, both with respect to speed and direction.  Infrasound signals (mb + mw) are not correlated with gravity waves.  The trace velocity of gw-signals indicates limits of infrasound detection capability (mw: V T {gw} < 10 m/s; mb: V T {gw} < 20 m/s).  The data of all infrasound stations, especially those which are linked to the peri-Antarctic belt, should to be analyzed on a broad frequency range including gw-signals (50 – 500 s). Conclusions II

23. Infrasound Technology Workshop – Tokyo, November 2007 23 Neumayer III research base L*W*H68*25*28 m 3 height above snow6 m weight2400 t floor space1900 m 2 ‘life-span’25 a Neumayer III L*D120*9 m 2 [2x] depth below snow-5 → 15 m floor space2000 m 2 ‘life-span’16 a Neumayer

24. Infrasound Technology Workshop – Tokyo, November 2007 24 Relocation of I27DE in 2008/09 Neumayer III will be built ~5 km to south of the current Neumayer research base the construction work for the new research base will be started this year a close schedule has to be kept (note, vessels call at the station only twice a year) cables for power supply of I27DE will be laid out this Antarctic summer I27DE will be relocated 2008/2009 (if the PTS will hopefully realize that Neumayer is not just around the corner)

25. Infrasound Technology Workshop – Tokyo, November 2007 25 Electric Power Supply at Neumayer III 3 * 30-kW horizontal axis wind turbines (< 100 dB aerodynamic noise) 3 blades, 30 rpm, 15 m tower height, and 5 m blade radius, BPH=1.5 Hz catabatic winds: ~180°, wind speed ~ 4 m/s easterly winds: ~90°, wind speed ~ 6 m/s 58 dB 54 dB